docs: def map(fun: Callable, xs: Iterable):
      """
      Traverse an iterable object applying function `fun`
      to each element and finally creats a workflow from it.
  
      :param fun:
        function to call in each element of the iterable
        object.
      :param xs:
        Iterable object.
  
      returns::py:class:`PromisedObject`
      """
      generator = (fun(x) for x in xs)
  
      return gather(*generator)